WASHINGTON, June 20 (Reuters) - Foes of the proposed Keystone XL pipeline, which would carry oil from Canada to Texas, said on Thursday that an expected White House package of proposals to combat climate change was not an adequate trade-off for approval of the controversial project.

Tom Steyer, a billionaire former hedge fund investor and environmental activist, said news that President Barack Obama would unveil a climate change strategy in the coming weeks, including curbs on power plant emissions, would be meaningless if the pipeline goes ahead.

"The idea of a trade here is very confusing and not logical," Steyer told reporters at the roll-out of a new social media campaign to engage Obama's grassroots supporters to ratchet up pressure to reject the pipeline.

Steyer's campaign is ramping up weeks after supporters of the pipeline launched their own media blitz urging the White House to approve the TransCanada Corp project.

Heather Zichal, Obama's energy and climate policy adviser, said on Wednesday that the president would use the federal Clean Air Act to clean up the country's power plants, which account for nearly 40 percent of domestic emissions.

The pipeline would link Alberta's oil sands production with refineries and ports along the U.S. Gulf Coast. The pipeline would transport about 830,000 barrels per day and cost some $5.3 billion to construct.

Obama is unlikely to make a final decision on the project before late this year or early 2014, and will rely on the recommendation of the State Department.

A State Department official said Thursday the agency is undergoing a rigorous process to evaluate the pipeline proposal.

"Time is required to do the job right, regardless of political pressure from either side," the official said, adding that the State Department is still trying to incorporate the input of over 1.2 million public comments on the project.

Environmental and civil rights activist Van Jones, who served as Obama's special adviser for green jobs in 2009, said crafting a tradeoff between a new climate policy and approval of Keystone would be a political "miscalculation" that would alienate Obama's supporters.